The invention relates to a method and a tool for material-removing machining a precisely fitting, cylindrical bore with high surface quality and a length that can be a multiple of the diameter from an existing bore with a finishing allowance related to the radius.
For the production of non-circular bores, e.g. bores with a square cross section, splines or wedge profile, broaches and broaching mandrels are used, which usually have several stepped, farther projecting cutting teeth staggered from front to back. Broaching tools are typically used for profiling, but not for finish machining and precision machining of cylindrical bore with high surface quality.
If cylindrical bores are to be finish-machined in the last processing step, reamers are used with which an existing bore that still has a reaming allowance of a few tenths of a mm, is drilled. Reaming is a relatively slow process, whereby the reamer is moved axially along the bore axis and simultaneously rotated. If the axial feed is e.g. 0.1 mm per revolution, i.e. 380 revolutions are needed for reaming a 38 mm long bore and the working speed is 800 rpm, the processing step takes about half a minute. The long processing time has a particularly strong impact when workpieces such as engines are produced on a large scale, with each workpiece having a large number of bores that need to be machined very precisely and with a high surface quality, for example, as guides for the intake and exhaust valves of the cylinders of a four- or six-cylinder engine.